New Industry Products

Nexperia Introduces ASFET MOSFETS Aimed at Hot-Swap Applications

August 27, 2021 by Gary Elinoff

The new application specific MOSFETS (ASFETs) are claimed to increase safe operating area (SOA) by 166%

Nexperia’s PSMN4R2-80YSE (80 V, 4.2 mΩ) and PSMN4R8-100YSE (100 V, 4.8 mΩ) ASFETs are made for hot-swap applications. The N-channel semiconductors are qualified to a maximum junction temperature of175℃, and are claimed to offer footprint size reductions of 80% and 75%, respectively.

The PSMN4R8-100YSE in its copper-clip, 5 x 6 x 1.1 mm LFPAK56E page. Image courtesy of datasheet


What are Application Specific ICs?

ASFETs are FETs specifically designed for specific applications, rather than for general applications. In a previously published article, Chris Boyce, Senior Director for the Power MOSFETs Group at Nexperia comments that “As designers push the boundaries of performance, it is crucial to understand how the MOSFET will be used in the application. There are 100+ parameters on a regular MOSFET datasheet but usually only a few are critical in each project.” He goes on to say that “By keeping individual application requirements front & centre of our thinking, we can choose to optimize the parameters that matter most in a particular use-case, often at the expense of others of less relevance.”


The Safe Operating Area

The PSMN4R2-80YSE and PSMN4R8-100YSE are ASFETs optimized for SOA, which is the amount of current and voltage the devices can safely handle, vital in instances of possible fast inrush current. In addition, the units avoid the ‘Spirito-knee’, whereby the SOA rapidly drops off with temperature.

As stated by Mike Becker, Senior International Product Marketing Manager at Nexperia: “SOA is traditionally only specified at 25 °C, meaning designers have to derate for operation in hot environments. Our new hot-swap ASFETs include a 125 °C SOA specification, eliminating this time-consuming task and confirming Nexperia’s excellent performance even at elevated temperatures”.


Design For Hot-Swapping

The two new ASFET MOSFETs have been specifically designed for hot-swapping, which means inserting plug-in boards into systems that must run continuously, 24 x 7, 365 days per year. An example cited by Nexperia is a 48V rack-based communications system.

Image courtesy of Nexperia

In the image above, consider Q1. When it turns on, as instructed by the hot-swap controller, it is vital that the inrush current is carefully controlled, to protect the plug-in board. This can be achieved by ASFETs such as the PSMN4R2-80YSE and PSMN4R8-100YSE, which are optimized for SOA. As a further benefit, both devices feature low RDS(ON)s for low I2R losses once the device is fully turned on.


The PSMN4R2-80YSE and PSMN4R8-100YSE

Complete information can be found at the PSMN4R2-80YSE datasheet and at the PSMN4R8-100YSE datasheet.

Drain Source Voltage (max) 80V 100V
Drain Current (max) 170A 120A
Total Pwr Dissipation (max) 294W 294W
RDS(ON) (maximum) 4.2mΩ 4.8mΩ
Gate-Drain Charge (typ) 11nC 15.3nC
Total Gate Charge (typ) 73nC 80nC
Recovered Charge (typ) 35nC 40nC



Aside from use in hot swap controllers, Nexperia’s new ASFETs can also successfully applied to:

  • Load switch
  • Soft start circuitry
  • Products that require E-fuse protection
  • Telecommunication systems that are powered via abased on a 48 volt backplane/supply rail


Regulatory and Safety

  • The maximum junction temperature of 175 °C meets IPC9592 regulations for industrial applications and telecoms.